1. Field of the Invention
The present invention relates generally to a system for recognizing driving condition of an automotive vehicle. The invention also relates to a shift control system for selecting the transmission speed ratio of an automatic power transmission utilizing the recognized vehicle driving condition.
2. Description of the Prior Art
In the automotive technologies, it is general or typical strategy for controlling various automotive installations, such as an internal combustion engine, a power train, a suspension system, a brake system and so forth, on the basis of a predetermined control constant in order to maintain vehicular driving parameters close to or at predetermined target values. As a result, control characteristics in various control are fixed at preset characteristics. For example, in the case of the internal combustion engine, a transition characteristic is fixed and determined by preset transition characteristics in an engine control system. Also, in the case of a transmission shift timing control, shift-up and shift-down timing for varying the transmission speed ratio is fixedly determined according to preset shifting characteristics associated with preselected transmission control parameters.
One of the typical types of shift control for the automotive automatic power transmission has been disclosed in Japanese Utility Model First (unexamined) Publication (Tokkai) Showa 62-194231. In the disclosure, a shift control system sets a shift pattern map in terms of preselected shift control parameters, such as an engine revolution speed, a throttle angular position and so forth. The shift control system thus selects transmission speed ratio on the basis of the shift control parameters according to the shift control characteristics set in the shift pattern map.
Such vehicular control systems encounter the drawback in optimizing control characteristics. Some examples will be listed herebelow.
When engine revolution asynchronous fuel supply, such is performed for various reason, such as for an acceleration enrichment for better engine response, engine jerking tends to occur under heavy traffic. On the other hand, when the transmission shift pattern is set principally for achieving good fuel economy, shift-up points at respective transmission speed ratio are set to cause up-shifting of the transmission speed ratio at unacceptably low engine speed to cause difficulty in sporty driving. Furthermore, by setting the transmission speed ratio for fuel economy, the transmission speed ratio shift-up and shift down operation is repeated frequently in heavy traffic to degrade drivability and riding comfort of the vehicle.
In contrast, it is natural demand of the drivers to adapt various control characteristics to be adapted to the vehicle or engine driving conditions. For instance, the driver tends to demand economical shift pattern in town road, powerful shift pattern in sporty driving, and a shift pattern having less occurrence of shifting in heavy traffic. In view of these, it is preferred to vary the transmission speed ratio shifting pattern depending upon vehicle driving condition and environmental conditions of the vehicle. For achieving this, it becomes essential to accurately detect the vehicle driving and environmental conditions for obtaining optimal control characteristics.